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LC is correct, but, I would run the thrust washer to be safe. It is common for the OMC props to slide up the prop shaft and damage the carrier. There is 2 or 3 mph in the outfit for sure. Try 72D jets, see if you can test a prop with less diameter 7000 to 7200 should be reachable. You can also try less timing 16. It is common for SOME 56 motors to run better. You can also try a surface or polar spark plug. Old trick to increase the compression. Some machined the plug so it ran without the washer. The plug extends farther into the chamber, reduces the volume of the chamber and the reduced volume increases compression.

Okay cool, thanks for the info Don. I was thinking about modding one of my thrust washers so that it will be thin enough to work with the omc cleaver. The prop i would be trying is almost an inch smaller diameter, does around a 500 rpm gain from switching from my 12.5" 24p cleaver to the 23 pitch cleaver sound about right

With performance props you need to try as many props as you can test. You can not go by prop sizes. Most times the prop performs different than expected and different on every boat. The key to testing is doing one small change at a time. Test and make notes. You are off to a very good start..70 mph is better than most. The best speed I have seen with your combo is 73 mph. And that owner spent lots of test time and money on props. My last advise is be careful! These boats were NOT designed to run 70 mph and you are well over their safe speed.

Yeah I definitely hear you on the safety side. It is a totally different animal then it was with the 49'er on it.
I dont think i would want to drive it without trim! Its amazing how little trim i use compared to my previous hulls. Im probably not going to do a ton more setup this year other then try the 23 cleaver out.

100% agreement!!!

Had the delta out a few more times, she pegs 71mph flat almost every pass. Im still only getting 65-6800 rpm WOT. I have not tried the 23 omc cleaver yet, im having serious issues with getting it to bolt up tight. I need an extra washer before the splines, the regular plastic one is not thick enough

We have the same issue with some of our OMC cleavers, if you don't run a thrust washer, put the plastic one on, then put a rubber washer ( we use the ones from a garden hose) on this will cover the rest of the exposed splines then put your prop nut on and snug it up. We only put ours on hand tight and then put the cotter pin in. Since we only run in forward the prop isn't going any where. You can also us an oversized washer that doesn't come into contact with the extra spline to take up the space then the prop nut.

Good idea with the rubber washer! I had done up an oversized washer this evening, not sure if tomorrow will work for testing or not

Your 71+/-mph Delta is a great lake and respectable racing speed; your reported 65-6800 large 300r swing @ 71 bit of a mystery. There should be <100r variation bt passes per water/wind conditions.
Sure, try different props. BUT,...be careful on chasing R's. If you want to crack 7K, to what end, +1mph? The smaller prop to get to 7K will get you to power band sooner for acceleration, not necessarily increase speed. You should not care about acceleration on the lake; it's of benefit racing exiting corner & first half of straight. Just remind yourself <6.8 will ensure engine longevity, >6.8 you're pushing envelope, chasing demons & one will bite.
We lake run/race voodoo ~68mph @ 6700r, low 135psi, Titus 12.5x24, it'll last forever(with oil,...sigh). We only race Critch ~74+ @ 6900r, 155psi with 91 @ 25:1, to ensure it lasts no lake running. There are faster boats, but it accelerates v well out of corners.
I've( & others) blown enuf engines to tell you that extra 100r,+,+ or 1mph,+,+ is not worth time and cost of rebuilding an engine that worked well enough, especially for lake running.
Swing the 24x 12.5 large prop at 71mph on the lake, keep r's down for longevity & speed where Don said it's safe, have fun.
PS: let us know how 23P prop performs:)

Typo "We" sb Kris!